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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

The dramatic role of astronomy in early modern drama

Coston, Micah Keith January 2017 (has links)
By examining five types of astronomical and celestial phenomena—comets, constellations, the zodiac, planets, and the music of the spheres—this thesis posits not only that early modern dramatists were influenced by established and emerging natural philosophy as habits of thought that manifested in their writing, but also that astronomical phenomena operate within the drama, performance, and in the theatre as elements for creating and developing a distinctly spatial dramaturgy. Using theories from the spatial turn, this thesis maps the positions, edges, disturbances, and motions of celestial properties within the imaginary and physical space of early modern drama and theatre. It argues that the case study plays examined within this thesis demonstrate a period-wide engagement, rather than an authorial-, company-, theatre-, or even genre-specific practice. Dramatists developed techniques using astronomical phenomena as dramatic methods that occasionally underscored early modern astronomical thought. However, in many cases constructed plots, characters, visual and sound effects, and movements transgressed astronomical expectations. Dramatists broke down constellations, inserted new stars in the heavens, created zodiacal females, launched pyrotechnical comets, moved planets unexpectedly across the stage, and played (and refrained from playing) celestial "music" for the audience. Recognising composite and often contradictory astronomical constructions within the drama, this thesis moves the critical discussion away from an intellectual history of natural philosophy and gravitates toward an active astronomical dramaturgy.
82

Stochastic description of rare events for complex dynamics in the Solar System / Modélisation stochastique d'événements rares dans des systèmes dynamiques complexes de notre système solaire

Woillez, Éric 21 September 2018 (has links)
Cette thèse considère quatre systèmes physiques complexes pour lesquels il est exceptionnellement possible d’identifier des variables lentes qui contrôlent l'évolution à temps long du système complet. La séparation d'échelle de temps entre ces variables lentes et les autres variables permet d'utiliser la technique de moyennisation stochastique pour obtenir une dynamique effective pour les variables lentes. Cette thèse considère la possibilité de prédire les événements rares dans le système solaire. Nous avons étudié deux types d’événements rares. Le premier est un renversement possible de l'axe de rotation de la Terre en l'absence des effets de marée de la Lune. Le second est la désintégration de l'ensemble du système solaire interne suite à une instabilité dans l'orbite de Mercure. Pour chacun des deux problèmes, il existe des variables lentes non triviales, qui ne sont pas données par des variables physiques naturelles. La moyennisation stochastique a permis de découvrir le mécanisme physique qui conduit à ces événements rares et de donner, par une approche purement théorique, l'ordre de grandeur de la probabilité de ces phénomènes. Nous avons également montré que la déstabilisation de Mercure sur un temps inférieur à l'âge du système solaire obéit à un mécanisme d'instanton bien décrit par la théorie des grandes déviations. Le travail effectué dans cette thèse ouvre donc un nouveau champ d'action pour l'utilisation d'algorithmes de calcul d'événements rares. Nous avons utilisé pour la première fois les théorèmes de moyennisation stochastique dans le cadre de la mécanique céleste pour quantifier l'effet stochastique des astéroïdes sur la trajectoire des planètes. Enfin, une partie du travail porte sur un problème de turbulence géophysique: dans l'atmosphère de Jupiter, on peut observer des structures zonales (jets) à grande échelles évoluant beaucoup plus lentement que les tourbillons environnants. Nous montrons qu'il est pour la première fois possible d'obtenir explicitement le profil de ces jets par moyennisation des degrés de liberté turbulents rapides. / The present thesis describes four complex dynamical systems. In each system, the long-term behavior is controlled by a few number of slow variables that can be clearly identified. We show that in the limit of a large timescale separation between the slow variables and the other variables, stochastic averaging can be performed and leads to an effective dynamics for the set of slow variables. This thesis also deals with rare events predictions in the solar system. We consider two possible rare events. The first one is a very large variation of the spin axis orientation of a Moonless Earth. The second one is the disintegration of the inner solar system because of an instability in Mercury’s orbit. Both systems are controlled by non-trivial slow variables that are not given by simple physical quantities. Stochastic averaging has led to the discovery of the mechanism leading to those rare events and gives theoretical bases to compute the rare events probabilities. We also show that Mercury’s short-term destabilizations (compared to the age of the solar system) follow an instanton mechanism, and can be predicted using large deviation theory. The special algorithms devoted to the computation of rare event probabilities can thus find surprising applications in the field of celestial mechanics. We have used for the first time stochastic averaging in the field of celestial mechanics to give a relevant orders of magnitude for the long-term perturbation of planetary orbits by asteroids. A part of the work is about geophysical fluid mechanics. In Jupiter atmosphere, large scale structures (jets) can be observed, the typical time of evolution of which is much larger than that of the surrounding turbulence. We show for the first time that the mean wind velocity can be obtained explicitly by averaging the fast turbulent degrees of freedom.
83

The Zulu literary artist's conception of celestial bodies and associated natural phenomena

Mathenjwa, L. F. (Langalibalele Felix), 1962- 11 1900 (has links)
This study gives the Zulu's views and ideas about celestial bodies and associated natural phenomena and how they illustrate features in both the oral and written literature. It sketches various focussing mainly on The concentration is conceptions about the whole universe celestial bodies and natural phenomena. on the sun, moon, stars, thunder and lightning in poetry and prose both modern and traditional. Emphasis is on the fact that Zulus do not perceive celestial bodies as mere bodies but assign certain beliefs and philosophies to them. In examining these different conceptions, Western as well as African literary theories have been used in this study. I~ ~r=rli~ional izibongo amakhosi are associated with the sun, the moon as well as the stars. Their warriors' attack is associated with the thunderstorm. These celestial bodies are also used as determinants of time in terms of day and night, seasons and different times for different daily chores. In modern poetry these bodies are mainly associated with God and in some instances they are referred to as God himself. In prose they are used as determinants of time and are also used figuratively to describe certain circumstances. The study gives an idea of how Zulus in general perceive these celestial bodies and natural phenomena. / African Languages / D.Litt. et Phil. (African Languages)
84

Dynamique des systèmes exoplanétaires / Exoplanetary Systems Dynamics

Faramaz, Virginie 16 October 2014 (has links)
Au moins 20% des étoiles de la séquence principale abritent des disques de débris, analogues à la ceinture de Kuiper. Ces disques sont la preuve que l'accumulation de solides a au moins permis la formation de corps de taille kilométrique. Il n'est donc pas surprenant que plusieurs de ces disques soient accompagnés de planètes, qui, en laissant leur empreinte dynamique sur la structure spatiale de ces disques, révèlent leur présence. Par conséquent, la détection d'un disque de débris excentrique entourant Zeta² Ret par le télescope spatial Herschel indique la présence d'un perturbateur massif dans ce système. Zeta² Ret étant un système mature, âgé de 2-3 Gyr, et en ce sens, analogue à notre propre système solaire, il offre un exemple différent d'évolution dynamique à long terme. Cette thèse comprend une modélisation détaillée de la structure du disque de débris de Zeta² Ret, ce qui conduit à des contraintes sur la masse et l'orbite du perturbateur suspecté. Cette étude révèle également que les structures excentriques dans les disques de débris peuvent survivre sur des échelles de temps Gyr.La modélisation de disques de débris peut permettre la découverte postérieure de planètes comme c'est le cas pour le système de Fomalhaut. La forme excentrique de son disque de débris fut d'abord attribuée à Fom b, un compagnon détecté près du bord interne du disque, mais qui se révèle finalement trop excentrique (e~0.6-0.9) pour lui donner sa forme, indiquant la présence d'un autre corps massif, Fom c. Le système planétaire qui en résulte est très instable, ce qui implique une diffusion récente de Fom b sur son orbite actuelle, éventuellement par Fom c. L'étude de ce scénario révèle qu'en ayant résidé dans une résonance de moyen-mouvement interne avec une Fom c excentrique et de masse comparable à Neptune ou Saturne, Fom b aurait subi une augmentation progressive de son excentricité sur des périodes comparables à l'âge du système (~440 Myr), ce qui l'aurait amenée assez proche de Fom c pour subir une diffusion récente, qui, complétée par une évolution séculaire avec Fom c, explique sa configuration orbitale actuelle. Ce mécanisme en trois étapes pourrait également avoir généré d'importantes quantités de matériel en orbites très excentriques, ce qui en retour pourrait alimenter en poussière les parties internes du système. Par conséquent, ce mécanisme pourrait aussi expliquer la présence de ceintures de poussières internes dans le système de Fomalhaut, mais aussi la découverte d'une importante population de ceintures de poussières chaudes et massives dans les systèmes âgés de plus de 100 Myr.Les systèmes planétaires découverts jusqu'ici présentent une grande variété d'architectures, et notre système solaire est loin d'être un modèle générique. Un des principaux mécanismes déterminant la morphologie d'un système planétaire est la migration planétaire. On attend d'un compagnon stellaire - ce que notre système solaire ne possède pas - qu'il affecte les conditions de migration planétaire, et conduise potentiellement à la formation de systèmes planétaires très différents. Ce phénomène est évidemment non négligeable puisque les systèmes binaires représentent au moins la moitié des systèmes stellaires. Dans les systèmes planétaires matures, la migration planétaire peut se produire suite à l'interaction avec le matériel solide et l'impact de la binarité sur cette migration tardive est exploré dans cette thèse. Un compagnon circumstellaire pourrait inverser la tendance à la migration interne des planètes dans les systèmes stellaires simples, et rapprocher ces planètes des régions perturbées par le compagnon binaire, où elles ne pourraient pas s'être formées in situ. Cela pourrait fournir une explication à la présence de planètes qui présentent des signes de migration externe vers un compagnon circumstellaire dans les systèmes de Gamma Cephei et HD 196885. / At least 20% of Main-Sequence stars are known to harbor debris disks analogs to the Kuiper Belt. These disks are proof that the accretion of solids has permitted the formation of at least km-sized bodies. It is thus not surprising that several of these disks are accompanied by planets, which may reveal themselves by setting their dynamical imprints on the spatial structure of debris disks. Therefore, the detection of an eccentric debris disk surrounding Zeta² Ret by the Herschel space telescope provides evidence for the presence of a massive perturber in this system.Zeta² Ret being a mature Gyr-old system, and in that sense, analogous to our own Solar System, it offers a different example of long-term dynamical evolution. This thesis includes a detailed modeling of the structure of the debris disk of Zeta² Ret, which leads to constraints on the mass and orbital characteristics of the putative perturber. This study also reveals that eccentric structures in debris disks can survive on Gyr timescales.Detailed modeling of the structure of debris disks can allow the posterior discovery of hidden planets as is the case for the Fomalhaut system. The eccentric shape of the debris disk observed around this star was first attributed to Fom b, a companion detected near the belt inner-edge, which revealed to be highly eccentric (e~0.6-0.9), and thus very unlikely shaping the belt. This hints at the presence of another massive body in this system, Fom c, which drives the debris disk shape. The resulting planetary system is highly unstable, which involves a recent scattering of Fom b on its current orbit, potentially with the yet undetected Fom c. This scenario is investigated in this thesis and its study reveals that by having resided in inner mean-motion resonance with a Neptune or Saturn-mass belt-shaping eccentric Fom c and therefore have suffered a gradual resonant eccentricity increase on timescales comparable to the age of the system (~440 Myr), Fom b could have been brought close enough to Fom c and suffered a recent scattering event, which, complemented by a secular evolution with Fom c, explains its current orbital configuration. This three-step scenario also implies that significant amounts of material may have been set on extremely eccentric orbits such as this of Fom b through this mechanism, which in return could feed in dust the inner parts of the system. Therefore, this mechanism may also explain the presence of inner dust belts in the Fomalhaut system, but also the discovery a significant population of very bright hot dust belts in systems older than 100 Myr.The planetary systems discovered so far exhibit a great variety of architectures, and our solar system is far from being a generic model. One of the main mechanism that determines a planetary system morphology is planetary migration. The presence of a stellar binary companion - which our solar system is deprived of - is expected to affect planetary migration conditions, and potentially lead to the formation of very different planetary systems. This phenomenon is obviously non-negligible since binary systems represent at least half of stellar systems. At late stages of planetary systems formation, planetary migration may occur as the result of interactions with remaining solid planetesimals and the impact of binarity on this planetesimal-driven migration is explored in this thesis. A stellar binary companion may in fact reverse the tendency for planets in single star systems to migrate inwards, and bring them closer to regions perturbed by the binary companion, where they could not have formed in situ. This may give an explanation for the presence of planets which present signs of outward migration towards a circumstellar companion in the Gamma Cephei and HD 196885 systems.
85

Simulação Gráfica de Buracos Negros utilizando Sistemas de Partículas

Cordeiro, Douglas Farias 17 March 2009 (has links)
The application of Computer Graphics tools in the nature phenomena simulation have been presenting a series of proposals since its creation. Over the years this task has gained a characteristic trait that makes it closer to the reality, both visually as by the abstraction strategies used. However, the specific application of this Computer Science area for the astrophysical phenomena simulation remains as something restricted explored, although the Computer Graphics is considered as an important tool to aid the synthesis of satellite images and the film industry. Accordingly, this graphical simulation area remains open in several ways, showing a need for development of simulation models for the phenomena described by Astrophysics. This dissertation presents a graphical simulation model of Black Holes, that is one of the most mysterious phenomena known by man, through the use of Particle Systems representation techniques and the approximation method Smoothed Particle Hydrodynamics, making possible this phenomenon observation and its application in the animations design. / A aplicação da Computação Gráfica na simulação de fenômenos da natureza tem apresentado, desde sua criação, uma série de propostas, que ao longo dos anos vem ganhando um caráter que as aproxima mais da realidade, tanto visualmente quanto através das estratégias de abstração utilizadas. Entretanto, a aplicação específica desta área da Ciência da Computação para a simulação de fenômenos astrofísicos fisicamente baseados ainda permanece como algo restritamente explorado, embora a Computação Gráfica seja considerada como uma importante ferramenta de auxílio a síntese de imagens obtidas via satélite e na industria cinematográfica. Neste sentido, esta área de simulação gráfica permanece em aberto sob diversos aspectos, denotando uma necessidade de concepção de modelos de simulação para os fenômenos descritos pela Astrofísica. Nesta dissertação será apresentado um modelo de simulação gráfica de Buracos Negros, um dos fenômenos mais misteriosos conhecidos pelo homem, através da utilização da técnica de representação Sistemas de Partículas e do método de aproximação Smoothed Particle Hydrodynamics, tornando possível a observação deste fenômeno e sua aplicação na concepção de animações. / Mestre em Ciência da Computação
86

Mythes, astronomie, découpage du temps et navigation traditionnelle : l’héritage océanien contenu dans les mots de la langue tahitienne / Myths, astronomy, dissecting time and traditional navigation : the oceanic heritage contained in the words of the tahitian language

Teriierooiterai, Claude 09 December 2013 (has links)
Comment les Tahitiens ont-ils conceptualisé le ciel pour en faire un instrument de mesure astronomique ? Leurs traditions apportent des explications sous forme de récits cosmogoniques. Ils peuvent nous envoûter mais, ils ne sont pas considérés comme des solutions scientifiques. L'astronomie a accordé aux théories qui ont cours aujourd'hui toutes les apparences du sérieux et de la rationalité. La cosmogonie a commencé le jour où l'homme s'est posé des questions sur son environnement et ses origines. Il fallait demander à ceux qui avaient voyagé, de raconter ce qu’ils avaient vu et entendu sur les régions encore plus lointaines. Les Tahitiens font partie de ces curieux qui sont allés voir ce qu’il y avait au-delà de l’horizon et pour qui la parole d’un ancêtre était acte de foi. Les réponses se trouvent donc dans les récits mythiques et le vocabulaire utilisé, à la source des symboles intellectuels. Pour les déchiffrer, l’approche linguistique est indispensable.Dans la cosmogonie tahitienne, le dieu Ta’aroa crée le monde. Le ciel demeure cependant uni à la terre, il le soulève à l’aide de dix piliers (pou), que repèrent des étoiles appelées ‘anā. Les objets célestes peuvent ainsi émerger des abysses à l’horizon et se mouvoir sur le dôme en traçant une dizaine de chemins (rua), guidés par les plus remarquables d’entre eux, les ta’urua. Cette conceptualisation du ciel offrira aux Tahitiens un instrument de mesure spatiotemporel remarquable.Leur lexique astronomique comporte près de deux cents termes porteurs de concepts. Les revisiter conduit à découvrir leur ancienne science. / How did the Tahitians conceptualize the skies in order to create their own instrument of astronomy? Traditions provide explanations in the form of cosmogony stories. They can entice or by no means are they considered scientific evidence. Astronomy has supported theories that give today a certain seriousness or rationality.Cosmogony began the day when man inquired about its environment and its origins. To fully understand, they asked those that have travelled in the past, recollecting descriptions of what they had seen and heard from faraway places.The curiosity of Tahitians has pushed them to travel beyond the horizon having only faith in the words of their ancestors. The answers can be found within the mythical recitals by understanding the vocabulary used at the source of intellectual symbols. Without a doubt, the approach of a linguist is necessary.In Tahitian cosmogony, the God Ta'aroa created the world. The sky was attached to the earth and in order to separate them; he used ten pillars "Pou", that are marked by stars in the sky called "'Anā". Celestial bodies move across the dome sky by following pathways called "Rua" and each pathway is highlighted by a dominant star called "Ta'urua". This conceptualization of the sky gave Tahitians a remarkable instrument for measuring space and time. The lexicon of astronomy terms numbers nearly two hundred. Understanding them leads one to discover their ancient science.
87

Manilius on the nature of the Universe : a study of the natural-philosophical teaching of the Astronomica

Colborn, Robert Maurice January 2015 (has links)
The thesis has two aims. The first is to show that a more charitable approach to Manilius, such as Lucretian scholarship has exhibited in recent decades, yields a wealth of exciting discoveries that earlier scholarship has not thought to look for. The thesis' contributions to this project centre on three aspects of the poem: (I) the sophistication of its didactic techniques, which draw and build on various predecessors in the tradition of didactic poetry; (II) its cosmological, physical and theological basis, which has no exact parallel elsewhere in either astrology or natural philosophy, and despite clear debts to various traditions, is demonstrably the invention of our poet; (III) the extent to which rationales and physical bases are offered for points of astrological theory – something unparalleled in other astrological texts until Ptolemy. The second, related aim of the thesis is to offer a more satisfying interpretation of the poem as a whole than those that have hitherto been put forward. Again the cue comes from Lucretius: though the DRN is at first sight primarily an exposition of Epicurean physics, it becomes clear that its principal concern is ethical, steering its reader away from superstition, the fear of death and other damaging thought-patterns. Likewise, the Astronomica makes the best sense when its principal message is taken to be not the set of astrological statements that make up its bulk, but the poem’s peculiar world- view, for which those statements serve as an evidential basis. It is, on this reading, just as much a poem ‘on the nature of the universe', which provides the title of my thesis. At the same time, however, it finds new truth in the conventional assumption that Manilius is first and foremost an advocate of astrology: it reveals his efforts to defend astrology at all costs, uncovers strategies for making the reader more amenable to further astrological study and practice, and contends that someone with Manilius' set of beliefs must first have been a devotee of astrology before embracing a natural- philosophical perspective such as his. The thesis is divided into prolegomena and commentaries, which pursue the aims presented above in two different but complementary ways. The prolegomena comprise five chapters, outlined below: Chapter 1 presents a comprehensive survey of the evidence for the cosmology, physics and theology of the Astronomica, and discovers that a coherent and carefully thought-out world-view underlies the poem. It suggests that this Stoicising world- view is drawn exclusively from a few philosophical works of Cicero, but is nonetheless the product of careful synthesis. Chapter 2 explores the relationship between this world-view and earlier Academic criticism of astrology and concludes that the former has been developed as a direct response to these criticisms, specifically as set out in Cicero’s De divinatione. Chapter 3 examines the later impact of Manilius’ astrological world-view, as far as it can be detected, assessing the evidence for the early reception of his poem and its role in the history of philosophical astrology. The overwhelming impression is that the work was received as a serious contribution to debate over the physical and theological underpinnings of astrology; its world-view was absorbed into the mainstream of astrological theory and directly targeted in the next wave of Academic criticism of astrology. Chapter 4 looks at the more subtle strategies of persuasion that are at work in the Astronomica. It observes, first, a number of structural devices and word- patternings that set up the poem as a model of the universe it describes. This first part of the chapter concludes by asking what didactic and/or philosophical purpose such modelling could serve. The second part examines how, by a gradual process of habituation-through-metaphor, the reader is made familiar with the conventional astrological way of thinking about the world, which might otherwise have struck him as a baffling mass of contradictions. The third part looks at the use of certain rhetorical figures, particularly paradox, to re-emphasise important physical claims and assist the process of habituation. Chapter 5 takes on the task of making sense of the Astronomica as a whole, seeking out an underlying rationale behind the choice and ordering of material, accounting as well as is possible for its apparently premature end, and asking why, if it is a serious piece of natural-philosophical teaching, it so often appears to be self- undermining. A short epilogue asks what path can have led Manilius to embark on such a work as the Astronomica. It offers a sketch of the author as an adherent (but not a practitioner) of astrology, who had developed a philosophical system first as scaffolding for an art under threat, but had then come to see more importance in that philosophical underpinning than in the activities of prediction. The lemmatised commentaries that follow cover several passages from the first book of the Astronomica. As crucial as the remaining four books are to his natural-philosophical teaching, it is in this part of the poem that Manilius concentrates the direct expositions of his world-view. Like the chapters, the commentaries' two concerns are the nature and the exposition of the work's world-view. Each of the commentaries has its own focus, but all make full use of the format to tease out the poet's teaching strategies and watch his techniques operate 'in real time' over protracted stretches of text. Finally, an appendix presents the case for the Astronomica as the earliest evidence for the use of plane-image star maps. At two points in his tour of the night sky Manilius describes the positions of constellations in a way that suggests that he is consulting a stereographic projection of each hemisphere, and that he is assuming his reader has one to hand, too. This observation casts valuable new light on the development of celestial cartography.
88

Himmlische Körper: Hintergrund und argumentative Funktion von 1Kor 15,40f

Klinghardt, Matthias 23 June 2020 (has links)
The coherent semantics of the sowing imagery (1Cor 15,36–44) suggest that heavenly bodies (v. 40–41) emerge from a process of body transformation, analogous to plants and animate beings (v. 37–39). The idea that the deceased are transformed into stars and thereby obtain a particular form of existence is widely attested in the mythography and in epitaphs of antiquity. In contrast to pagan conceptions about the dead permanently returning into celestial spheres, the heavenly bodies according to Paul represent a postmortem, albeit a pre-resurrection, stage in the development of human bodies. Accordingly, the heavenly body represents an intermediary ontological mode between the animated body of earthly creatures and the spiritual body of resurrection.
89

Stabilitätsuntersuchungen an Asteroidenbahnen in ausgewählten Bahnresonanzen des Edgeworth-Kuiper-Gürtels

Gerlach, Enrico 24 October 2008 (has links)
Gegenstand dieser Dissertation ist eine umfassende Analyse der Stabilität von Asteroidenbahnen im Edgeworth-Kuiper-Gürtel am Beispiel der 3:5-, 4:7- und der 1:2-Bahnresonanz mit Neptun. Einen weiteren Schwerpunkt der Arbeit bildet die Untersuchung der numerischen Berechenbarkeit der Lyapunov-Zeit von Asteroidenbahnen. Ausgehend von einer allgemeinen Beschreibung der bei numerischen Berechnungen auftretenden Rundungs- und Diskretisierungsfehler wird deren Wachstum bei numerischen Integrationen ermittelt. Diese, teilweise maschinenabhängigen, Fehler beeinflussen die berechnete Trajektorie des Asteroiden ebenso wie die daraus abgeleitete Lyapunov-Zeit. Durch Beispielrechnungen mit unterschiedlichen Rechnerarchitekturen und Integrationsmethoden wird der Einfluss auf die erhaltenen Lyapunov-Zeiten eingehend untersucht. Als Maß zur Beschreibung dieser Abhängigkeit wird ein Berechenbarkeitsindex $\kappa$ definiert. Weiterhin wird gezeigt, dass die allgemeine Struktur des Phasenraumes robust gegenüber diesen Änderungen ist. Unter Nutzung dieser Erkenntnis werden anschließend ausgewählte Bahnresonanzen im Edgeworth-Kuiper-Gürtel untersucht. Grundlegende Charakteristika, wie die Resonanzbreiten, werden dabei aus einfachen Modellen abgeleitet. Eine möglichst realitätsnahe Beschreibung der Stabilität wird durch numerische Integration einer Vielzahl von Testkörpern zusammen mit den Planeten Jupiter bis Neptun erreicht. Die erhaltenen Ergebnisse werden dabei mit der beobachteten Verteilung der Asteroiden im Edgeworth-Kuiper-Gürtel verglichen. ---- Hinweis: Beim Betrachten der pdf-Version dieses Dokumentes mit dem Acrobat Reader mit einer Version kleiner 8.0 kann es unter Windows zu Problemen in der Darstellung der Abbildungen auf den Seiten 46, 72, 74, 79 und 86 kommen. Um die Datenpunkte zu sehen ist eine Vergrößerung von mehr als 800% notwendig. Alternativ kann in den Grundeinstellungen der Haken für das Glätten von Vektorgraphiken entfernt werden. / This dissertation presents a comprehensive description of the stability of asteroid orbits in the Edgeworth-Kuiper belt taking the 3:5, 4:7 and 1:2 mean motion resonance with Neptune as example. Further emphasis is given to the numerical computability of the Lyapunov time of asteroids. Starting with a general description of rounding and approximation errors in numerical computations, the growth of these errors within numerical integrations is estimated. These, partly machine-dependent errors influence the calculated trajectory of the asteroid as well as the derived Lyapunov time. Different hardware architectures and integration methods were used to investigate the influence on the computed Lyapunov time. As a measure of this dependence a computability index $\kappa$ is defined. Furthermore it is shown, that the general structure of phase space is robust against these changes. Subsequently, several selected mean motion resonances in the Edgeworth-Kuiper belt are investigated using these findings. Basic properties, like the resonance width, are deduced from simple models. To get a realistic description of the stability, a huge number of test particles was numerically integrated together with the planets Jupiter to Neptune. The obtained results are compared to the observed distribution of asteroids in the Edgeworth-Kuiper belt. ---- Additional information: If the pdf-file of this document is viewed using Acrobat Reader with a version less 8.0 under Windows the figures on page 46, 72, 74, 79 and 86 are shown incomplete. To see the data points a zoom factor larger than 800% is necessary. Alternatively the smoothing of vector graphics should be disabled in the settings of the reader.
90

Use of two-way time transfer measurements to improve geostationary satellite navigation :

Dainty, Benjamin G. 2007 March 1900 (has links)
Thesis (M.S.)-- Air Force Institute of Technology. / The original document contains color images.

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